blog_theme/partials/post-media.hbs

{{#if feature_image}}
    <div class="post-media">
        <div
            class="u-placeholder{{#if same_height}} same-height {{ratio}}{{/if}}">
            <a class="post-image-link" href="{{url}}">
                <img class="post-image lazyload{{#if same_height}} u-object-fit{{/if}}"
                    data-srcset="{{img_url feature_image size="s"}} 400w, {{img_url feature_image size="m"}} 750w, {{img_url feature_image size="l"}} 960w"
                    src="data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw=="
                    data-sizes="auto" alt="{{title}}">
            </a>
        </div>
    </div>
{{/if}}